Days sales outstanding (DSO) is the average number of days between issuing an invoice and collecting payment. It is calculated as accounts receivable divided by average daily sales, expressed in days. Lower DSO means faster collections and less working capital tied up in unpaid invoices. Industry benchmarks vary widely, but for most B2B SMBs, DSO between 30 and 45 days is healthy.
DSO is one of the cleanest measures of working capital efficiency on the receivables side. A 30-day DSO means customers pay, on average, 30 days after invoicing — which lines up with standard net-30 terms. DSO of 60 means customers are routinely paying twice as slow as terms allow, which signals a collections problem (or terms creep). Movements in DSO drive movements in cash directly: if DSO increases by 10 days on $2M of annual revenue, roughly $55K of additional cash is locked up in receivables. DSO is also a leading indicator — when DSO drifts up over two or three months, it almost always precedes broader cash pressure.
DSO (days) = (Accounts Receivable ÷ Total Credit Sales for Period) × Number of Days in Period
DSO is the single most actionable cash metric for B2B businesses. Every day of DSO improvement on a $5M revenue business is worth roughly $13,700 of permanent additional cash. Most owners discover DSO is rising only after cash gets tight — at which point a quarter has already been lost. Watching DSO weekly means catching the slowdown early, when phone calls and tightened terms still work. DSO trend also reveals customer health: a major customer paying slower is often the first sign of their financial trouble.
Fynso tracks DSO weekly by customer, customer segment, and overall, surfacing both the absolute number and the trend. When DSO drifts up, the daily brief breaks down which customers are responsible — usually a small number of accounts driving most of the slowdown. Fynso drafts tone-matched follow-up emails for those specific customers based on payment history (firmer for repeat late payers, softer for trusted ones) and flags whether tightening terms makes sense given the customer's pattern. The result is that DSO becomes a managed metric rather than a passively observed one.
Professional services
An agency with $3M of annual revenue, $250K of AR, runs DSO of about 30 days — right at terms. If DSO drifts to 45 days, an additional $125K is locked up in AR — money that could have funded a hire or a marketing push.
Medical practices
A medical practice billing insurance runs much higher DSO — often 45–75 days — because insurance carrier processing time is built into the cycle. The right benchmark for medical is the spread between insurance and patient-pay DSO; patient-pay DSO over 60 days signals a collection process failure rather than a payor mix issue.
Construction
A general contractor frequently has DSO above 60 days because of progress billing cycles and retainage. Tracking DSO by project type (residential vs commercial vs government) reveals which mix takes longest to convert — useful for both bidding and working capital planning.
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